<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>事件处理方式</title>
    <style>
        .wrapper{
            width: 500px;
            height:300px;
            background-color: #f00;
        }
        .content{
            width: 300px;
            height: 150px;
            background-color: green;
        }
        .box{
            width: 100px;
            height: 100px;
            background-color: #5fd;
        }
    </style>
</head>
<body>
    <div class="wrapper">
        <div class="content">
            <div class="box">
            </div>
        </div>
    </div>
</body>
</html>
<script>
    let wrapper = document.getElementsByClassName('wrapper')[0]
    let content = 
</script>